The popularity and convenience of the Internet has resulted in the reinvention of traditional telephony services. These services are offered over a packet switched network with minimal or no cost to the users. IP (Internet Protocol) telephony, thus, have found significant success, particularly in the long distance market. In general, IP telephony, which is also referred to as Voice-over-IP (VOIP), is the conversion of voice information into data packets that are transmitted over an IP network. Users also have turned to IP telephony as a matter of convenience in that both voice and data services are accessible through a single piece of equipment, namely a personal computer. The continual integration of voice and data services further fuels this demand for IP telephony applications. One important area of call processing is billing, particularly when the call is established over a data network with many possible call paths.
The Session Initiation Protocol (SIP) has emerged to address the signaling of calls over an IP network. As an end-to-end protocol, SIP advantageously permits the end nodes with the capability to control call processing. By contrast, traditional telephony services are totally controlled by the intermediate network components; that is, the switches have full control over call establishment, switching, and call termination. In the SIP architecture, it is sometimes desirable for an intermediate network element to control the call processing, particularly as it relates to billing.
For example, in the Public Switched Telephone Network (PSTN), a caller is billed based on the phone number that they dial to originate the call. In most cases, the caller pays for calls that they originate. With great difficulty and expense, more creative charging models have been developed in the PSTN, including 800 service, 900 service, etc. However, no mechanism exists for a caller to find out how much a particular call will cost until after the fact—i.e., usually, when the bill arrives.
Therefore, there is a need for an approach for timely notifying a caller of the charges associated with a voice call over a data network. There is also a need to provide telephony services economically. Further, there is also a need to preserve a standard architecture to promote deployment of network services.